The McDonald Accelerating Stars Survey (MASS): Architecture of the Ancient Five-Planet Host System Kepler-444

Abstract

We present the latest and most precise characterization of the architecture for the ancient ($\approx 11$ Gyr) Kepler-444 system, which is composed of a K0 primary star (Kepler-444 A) hosting five transiting planets, and a tight M-type spectroscopic binary (Kepler-444 BC) with an A-BC projected separation of 66 au. We have measured the system's relative astrometry using the adaptive optics imaging from Keck/NIRC2 and Kepler-444 A's radial velocities from the Hobby Eberly Telescope, and re-analyzed relative radial velocities between BC and A from Keck/HIRES. We also include the Hipparcos-Gaia astrometric acceleration and all published astrometry and radial velocities into an updated orbit analysis of BC's barycenter. These data greatly extend the time baseline of the monitoring and lead to significant updates to BC's barycentric orbit compared to previous work, including a larger semi-major axis ($a=52.2_{-2.7}^{+3.3}$ au), a smaller eccentricity ($e=0.55\pm 0.05$), and a more precise inclination ($i=85.4_{-0.4}^{+0.3}$ degrees). We have also derived the first dynamical masses of B and C components. Our results suggest Kepler-444~A's protoplanetary disk was likely truncated by BC to a radius of $\approx 8$ au, which resolves the previously noticed tension between Kepler-444 A's disk mass and planet masses. Kepler-444 BC's barycentric orbit is likely aligned with those of A's five planets, which might be primordial or a consequence of dynamical evolution. The Kepler-444 system demonstrates that compact multi-planet systems residing in hierarchical stellar triples can form at early epochs of the Universe and survive their secular evolution throughout cosmic time.

arXiv commentAJ in press

References in corpus (77)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
• A Survey of Stellar Families: Multiplicity of Solar-Type Stars
• Stellar Multiplicity
• Exploring the Milky Way stellar disk. A detailed elemental abundance study of 714 F and G dwarf stars in the Solar neighbourhood
• Architecture and Dynamics of Kepler's Candidate Multiple Transiting Planet Systems
• Kepler-16: A Transiting Circumbinary Planet
• Probabilistic Forecasting of the Masses and Radii of Other Worlds
• Gravitational Instabilities in Circumstellar Disks
• The LCES HIRES/Keck Precision Radial Velocity Exoplanet Survey
• The California Planet Survey I. Four New Giant Exoplanets
• Secular Dynamics in Hierarchical Three-Body Systems
• Ages and fundamental properties of Kepler exoplanet host stars from asteroseismology
• Spectral Properties of Cool Stars: Extended Abundance Analysis of 1617 Planet Search Stars
• A Planetary Companion to gamma Cephei A
• Dynamic temperature selection for parallel-tempering in Markov chain Monte Carlo simulations
• The Hipparcos-Gaia Catalog of Accelerations: Gaia EDR3 Edition
• Make Super-Earths, Not Jupiters: Accreting Nebular Gas onto Solid Cores at 0.1 AU and Beyond
• The Impact of Stellar Multiplicity on Planetary Systems, I.: The Ruinous Influence of Close Binary Companions
• Improving Galactic Center Astrometry by Reducing the Effects of Geometric Distortion
• A Triple Protostar System Formed via Fragmentation of a Gravitationally Unstable Disk
• The Hipparcos-Gaia Catalog of Accelerations
• Inside-Out Planet Formation
• A Comprehensive Study of the Kepler Triples via Eclipse Timing
• An ancient extrasolar system with five sub-Earth-size planets
• A Guide to Realistic Uncertainties on Fundamental Properties of Solar-Type Exoplanet Host Stars
• Observational Implications of Precessing Protostellar Discs and Jets
• The California-Kepler Survey. II. Precise Physical Properties of 2025 Kepler Planets and Their Host Stars
• Tidal Truncation of Inclined Circumstellar and Circumbinary Discs in Young Stellar Binaries
• The formation of close binary systems
• Ten Year Review of Queue Scheduling of the Hobby-Eberly Telescope
• Influence of Stellar Multiplicity On Planet Formation. I. Evidence of Suppressed Planet Formation Due to Stellar Companions Within 20 AU and Validation of Four Planets From the Kepler Multiple Planet Candidates
• Photometric Amplitude Distribution of Stellar Rotation of Kepler KOIs-Indication for Spin-Orbit Alignment of Cool Stars and High Obliquity for Hot Stars
• Relative velocities among accreting planetesimals in binary systems: the circumprimary case
• Impact of Binary Stars on Planet Statistics -- I. Planet Occurrence Rates, Trends with Stellar Mass, and Wide Companions to Hot Jupiter Hosts
• Exploring the alpha-enhancement of metal-poor planet-hosting stars. The Kepler and HARPS samples
• orvara: An Efficient Code to Fit Orbits using Radial Velocity, Absolute, and/or Relative Astrometry
• The Degree of Alignment Between Circumbinary Disks and Their Binary Hosts
• A Keck HIRES Doppler Search for Planets Orbiting Metal-Poor Dwarfs. II. On the Frequency of Giant Planets in the Metal-Poor Regime
• Observational constraints on dust disk sizes in tidally truncated protoplanetary disks in multiple systems in the Taurus region
• Weakened magnetic braking supported by asteroseismic rotation rates of Kepler dwarfs
• Tidal Torques on Misaligned Disks in Binary Systems
• SPIRou Input Catalogue: Global properties of 440 M dwarfs observed with ESPaDOnS at CFHT
• Astrometric Monitoring of the HR 8799 Planets: Orbit Constraints from Self-Consistent Measurements
• Orbital Architectures of Planet-Hosting Binaries: I. Forming Five Small Planets in the Truncated Disk of Kepler-444A
• Spin-orbit alignment of exoplanet systems: ensemble analysis using asteroseismology
• Fine structure in the phase space distribution of nearby subdwarfs
• Planet formation in binaries: dynamics of planetesimals perturbed by the eccentric protoplanetary disk and the secondary
• Planet formation in stellar binaries I: planetesimal dynamics in massive protoplanetary disks
• Direct Imaging Discovery and Dynamical Mass of a Substellar Companion Orbiting an Accelerating Hyades Sun-like Star with SCExAO/CHARIS
• The velocity distribution of nearby stars from Hipparcos data I. The significance of the moving groups
• SOAR TESS Survey. II: The impact of stellar companions on planetary populations
• Orbit and Dynamical Mass of the Late-T Dwarf Gl 758 B
• SCExAO/CHARIS Direct Imaging Discovery of a 20 au Separation, Low-Mass Ratio Brown Dwarf Companion to an Accelerating Sun-like Star
• Compact multi-planet systems are more common around metal poor hosts
• Stellar ages, masses and radii from asteroseismic modeling are robust to systematic errors in spectroscopy
• Orbital Parameter Determination for Wide Stellar Binary Systems in the Age of Gaia
• Orbital Architectures of Planet-Hosting Binaries II. Low Mutual Inclinations Between Planetary and Stellar Orbits
• Effects of Disk Warping on the Inclination Evolution of Star-Disk-Binary Systems
• Stellar Companions to TESS Objects of Interest: A Test of Planet-Companion Alignment
• A Possible Alignment Between the Orbits of Planetary Systems and their Visual Binary Companions
• Dynamical Mass of the Young Substellar Companion HD 984 B
• Dancing twins: stellar hierarchies that formed sequentially?
• Mass, Density, and Formation Constraints in the Compact, Sub-Earth Kepler-444 System including Two Mars-Mass Planets
• The Young Substellar Companion ROXs 12 B: Near-Infrared Spectrum, System Architecture, and Spin-Orbit Misalignment
• Results from The COPAINS Pilot Survey: four new brown dwarfs and a high companion detection rate for accelerating stars
• A coplanar circumbinary protoplanetary disk in the TWA 3 triple M dwarf system
• The spin-orbit alignment of visual binaries
• The McDonald Accelerating Stars Survey (MASS): White Dwarf Companions Accelerating the Sun-like Stars 12 Psc and HD 159062
• The McDonald Accelerating Stars Survey (MASS): Discovery of a Long-Period Substellar Companion Orbiting the Old Solar Analog HD 47127
• A New Method for Target Selection in Direct Imaging Programs with COPAINS
• From large-scale to protostellar disk fragmentation into close binary stars
• The Gliese 86 Binary System: A Warm Jupiter Formed in a Disk Truncated at $\approx$2 AU

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• The Kepler Giant Planet Search. I: A Decade of Kepler Planet-host Radial Velocities from W. M. Keck Observatory
• Inner Planetary System Gap Complexity is a Predictor of Outer Giant Planets
• Dynamical Architectures of S-type Transiting Planets in Binaries I: Target Selection using Hipparcos and Gaia proper motion anomalies
• Dynamical Architectures of S-type Transiting Planets in Binaries II: A Dichotomy in Orbital Alignment of Small Planets in Close Binary Systems